As far as I understand, the LiMn2O4 has 8 formula units in one unit cell, so you definitely need 56 atoms in the unit cell.
The cif file contains only information on the inequivalent atoms, all others can be obtained from the former by applying the coordinate transformation of the space group Fd-3m A useful way to do that, as specified here: http://www.quantum-espresso.org/faq/input-data/#3.2 <http://www.quantum-espresso.org/faq/input-data/#3.2> is to run the converter from cif files included in the QE distribution. espresso-5.2.0/PW/tools/cif2qe.sh 1513984 > 1513984.scf.in This produces a file (that you might want to check for correctness and to modify according to your needs) that looks like &CONTROL title = '1513984' calculation = 'relax' restart_mode = 'from_scratch' outdir = './1' pseudo_dir = '../PP/atompaw' prefix = '1513984' disk_io = 'none' verbosity = 'default' etot_conv_thr = 0.0001 forc_conv_thr = 0.001 nstep = 400 tstress = .true. tprnfor = .true. / &SYSTEM ibrav = 0 nat = 56 ntyp = 3 ecutwfc = 60 ecutrho = 480 vdw_corr = 'xdm' xdm_a1 = 1.2153 xdm_a2 = 2.3704 / &ELECTRONS electron_maxstep = 200 conv_thr = 1.0D-7 diago_thr_init = 1e-4 startingpot = 'atomic' startingwfc = 'atomic' mixing_mode = 'plain' mixing_beta = 0.5 mixing_ndim = 8 diagonalization = 'david' / &IONS ion_dynamics = 'bfgs' / ATOMIC_SPECIES Li1+ 0.0000000000 Li1+.pw86pbe-n-kjpaw_psl.1.0.0.UPF Mn3.5+ 0.0000000000 Mn3.5+.pw86pbe-n-kjpaw_psl.1.0.0.UPF O2- 0.0000000000 O2-.pw86pbe-n-kjpaw_psl.1.0.0.UPF ATOMIC_POSITIONS crystal Li1+ 0.87500000000000 0.87500000000000 0.87500000000000 Li1+ 0.12500000000000 0.12500000000000 0.12500000000000 Li1+ 0.87500000000000 0.37500000000000 0.37500000000000 Li1+ 0.37500000000000 0.87500000000000 0.37500000000000 Li1+ 0.37500000000000 0.37500000000000 0.87500000000000 Li1+ 0.12500000000000 0.62500000000000 0.62500000000000 Li1+ 0.62500000000000 0.12500000000000 0.62500000000000 Li1+ 0.62500000000000 0.62500000000000 0.12500000000000 Mn3.5+ 0.50000000000000 0.25000000000000 0.25000000000000 Mn3.5+ 0.25000000000000 0.50000000000000 0.25000000000000 Mn3.5+ 0.25000000000000 0.25000000000000 0.50000000000000 Mn3.5+ 0.50000000000000 0.50000000000000 0.50000000000000 Mn3.5+ 0.50000000000000 0.75000000000000 0.75000000000000 Mn3.5+ 0.75000000000000 0.50000000000000 0.75000000000000 Mn3.5+ 0.75000000000000 0.75000000000000 0.50000000000000 Mn3.5+ 0.00000000000000 0.25000000000000 0.75000000000000 Mn3.5+ 0.00000000000000 0.75000000000000 0.25000000000000 Mn3.5+ 0.25000000000000 0.00000000000000 0.75000000000000 Mn3.5+ 0.75000000000000 0.00000000000000 0.25000000000000 Mn3.5+ 0.25000000000000 0.75000000000000 0.00000000000000 Mn3.5+ 0.75000000000000 0.25000000000000 0.00000000000000 Mn3.5+ 0.50000000000000 0.00000000000000 0.00000000000000 Mn3.5+ 0.00000000000000 0.50000000000000 0.00000000000000 Mn3.5+ 0.00000000000000 0.00000000000000 0.50000000000000 O2- 0.73730000000000 0.01270000000000 0.01270000000000 O2- 0.01270000000000 0.73730000000000 0.01270000000000 O2- 0.01270000000000 0.01270000000000 0.73730000000000 O2- 0.73730000000000 0.73730000000000 0.73730000000000 O2- 0.26270000000000 0.98730000000000 0.98730000000000 O2- 0.98730000000000 0.26270000000000 0.98730000000000 O2- 0.98730000000000 0.98730000000000 0.26270000000000 O2- 0.26270000000000 0.26270000000000 0.26270000000000 O2- 0.73730000000000 0.51270000000000 0.51270000000000 O2- 0.23730000000000 0.01270000000000 0.51270000000000 O2- 0.23730000000000 0.51270000000000 0.01270000000000 O2- 0.01270000000000 0.23730000000000 0.51270000000000 O2- 0.51270000000000 0.73730000000000 0.51270000000000 O2- 0.51270000000000 0.23730000000000 0.01270000000000 O2- 0.01270000000000 0.51270000000000 0.23730000000000 O2- 0.51270000000000 0.01270000000000 0.23730000000000 O2- 0.51270000000000 0.51270000000000 0.73730000000000 O2- 0.73730000000000 0.23730000000000 0.23730000000000 O2- 0.23730000000000 0.73730000000000 0.23730000000000 O2- 0.23730000000000 0.23730000000000 0.73730000000000 O2- 0.26270000000000 0.48730000000000 0.48730000000000 O2- 0.76270000000000 0.98730000000000 0.48730000000000 O2- 0.76270000000000 0.48730000000000 0.98730000000000 O2- 0.98730000000000 0.76270000000000 0.48730000000000 O2- 0.48730000000000 0.26270000000000 0.48730000000000 O2- 0.48730000000000 0.76270000000000 0.98730000000000 O2- 0.98730000000000 0.48730000000000 0.76270000000000 O2- 0.48730000000000 0.98730000000000 0.76270000000000 O2- 0.48730000000000 0.48730000000000 0.26270000000000 O2- 0.26270000000000 0.76270000000000 0.76270000000000 O2- 0.76270000000000 0.26270000000000 0.76270000000000 O2- 0.76270000000000 0.76270000000000 0.26270000000000 K_POINTS automatic 2 2 2 0 0 0 CELL_PARAMETERS 15.57115429380366 0.00000000000000 0.00000000000000 0.00000000000000 15.57115429380366 0.00000000000000 0.00000000000000 0.00000000000000 15.57115429380366 Giovanni > On 06 Jul 2015, at 20:51, max <[email protected]> wrote: > > Hello, > > I'm confusing, I need to do some convergence test, but I don't know if I need > primitive or one unit cell and how to select it. > > I'm using this structure http://www.crystallography.net/cod/1513984.html > <http://www.crystallography.net/cod/1513984.html> > > I extracted the crystallographic translation. The cell formula units are 8, > has 56 atoms. See ATOMIC_POSITIONS bellow. > > One unit cell of LiMn2O4 (spinel) has 7 atoms. > > I have the following questions: > > Do I need to put 7 atoms in the primitive cell or how many? > > How can I select the atoms position for primitive or one unit cell? > > ATOMIC_POSITIONS alat > Li 0.125000000 0.125000000 0.125000000 > Li -0.125000000 0.875000000 0.875000000 > Li 0.875000000 -0.125000000 0.875000000 > Li 0.875000000 0.875000000 -0.125000000 > Li -0.125000000 -0.125000000 -0.125000000 > Li -0.125000000 0.375000000 0.375000000 > Li 0.375000000 0.875000000 0.375000000 > Li 0.875000000 0.375000000 0.375000000 > Mn 0.500000000 0.500000000 0.500000000 > Mn -0.500000000 1.250000000 1.250000000 > Mn 1.250000000 -0.500000000 1.250000000 > Mn 1.250000000 1.250000000 -0.500000000 > Mn -0.500000000 -0.500000000 -0.500000000 > Mn 0.500000000 -0.250000000 -0.250000000 > Mn -0.250000000 0.500000000 -0.250000000 > Mn -0.250000000 -0.250000000 0.500000000 > Mn -0.500000000 0.750000000 0.750000000 > Mn 0.000000000 1.250000000 0.750000000 > Mn 0.000000000 0.750000000 1.250000000 > Mn 1.250000000 0.000000000 0.750000000 > Mn 0.750000000 -0.500000000 0.750000000 > Mn 0.750000000 0.000000000 1.250000000 > Mn 1.250000000 0.750000000 0.000000000 > Mn 0.750000000 1.250000000 0.000000000 > O -0.262700000 1.012700000 1.012700000 > O 1.012700000 -0.262700000 1.012700000 > O 1.012700000 1.012700000 -0.262700000 > O -0.262700000 -0.262700000 -0.262700000 > O 0.262700000 -0.012700000 -0.012700000 > O -0.012700000 0.262700000 -0.012700000 > O -0.012700000 -0.012700000 0.262700000 > O 0.262700000 0.262700000 0.262700000 > O -0.262700000 0.512700000 0.512700000 > O 0.237300000 1.012700000 0.512700000 > O 0.237300000 0.512700000 1.012700000 > O 1.012700000 0.237300000 0.512700000 > O 0.512700000 -0.262700000 0.512700000 > O 0.512700000 0.237300000 1.012700000 > O 1.012700000 0.512700000 0.237300000 > O 0.512700000 1.012700000 0.237300000 > O 0.512700000 0.512700000 -0.262700000 > O -0.262700000 0.237300000 0.237300000 > O 0.237300000 -0.262700000 0.237300000 > O 0.237300000 0.237300000 -0.262700000 > O 0.262700000 0.487300000 0.487300000 > O 0.762700000 -0.012700000 0.487300000 > O 0.762700000 0.487300000 -0.012700000 > O -0.012700000 0.762700000 0.487300000 > O 0.487300000 0.262700000 0.487300000 > O 0.487300000 0.762700000 -0.012700000 > O -0.012700000 0.487300000 0.762700000 > O 0.487300000 -0.012700000 0.762700000 > O 0.487300000 0.487300000 0.262700000 > O 0.262700000 0.762700000 0.762700000 > O 0.762700000 0.262700000 0.762700000 > O 0.762700000 0.762700000 0.262700000 > > -- > Máximo Ramírez > Physics Degree > Universidad Autónoma de Santo Domingo > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: http://people.na.infn.it/~cantele
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